The present invention relates to a method of producing a composite diamond body comprising the addition of diamond particles, and powder(s) forming the binder phase comprising cobalt, wherein the cobalt powder has mainly a face centered cubic (fcc) structure. The present invention also relates to a composite diamond body made according to the method of the invention.
Depending on composition and grain size, a wide range of diamond materials can be used in many applications, for instance in rock drilling, metal cutting tools and in wear parts. Examples of materials to be machined are concrete, metals, and natural stone such as granite, marble, sandstone, limestone, etc. Usually, due to its brittleness, composite diamond bodies are preferably placed onto a substrate with a higher toughness, for example cemented carbide or metal, often during the manufacturing of the composite diamond body.
The use of cobalt as a binder phase when manufacturing composite diamond bodies is well known in the art.
Cobalt is allotropic, that is, at temperatures less than about 417° C., pure cobalt atoms are arranged in a hexagonal close packed (hcp) structure and at temperatures above about 417° C., pure cobalt atoms are arranged in a face centered cubic (fcc) structure. Thus, above 417° C., pure cobalt exhibits an allotropic transformation, i.e., the hcp-structure changes to fcc-structure.
The cobalt powder conventionally used when manufacturing composite diamond bodies mainly has an hcp-structure. However, in a sintered body, the cobalt binder phase has an fcc-structure which is obtained during the sintering operation or the hot pressing operation.
During manufacturing of composite diamond bodies it is important that the cobalt powder is easily dispersed during mixing.
One of the important properties for composite diamond tool making is good pressing properties, i.e., the ability of achieve high density in the pressed body. Powders which are able to be pressed into bodies having high density will have less pores which is an advantage since pores can cause problems during machining.
It is also an advantage to have a high strength of the pressed body since it makes it less prone to crack or be deformed during handling.
A common phenomenon when making composite diamond bodies is that the hardness decreases when high sintering temperatures are used. A high sintering temperature is, for example, beneficial when tungsten carbide is added to improve the hardness and the wear properties.
Also, there is a constant need for improving the tool life of the composite diamond containing tools. Longer tool life is a great advantage in many applications since changing tools is a very time consuming step. An increased hardness of the composite diamond tool improves the tool life.